边石坝是由洞底流水成因的景观，当富含钙离子的水流经凹凸不平的洞底时，在凸起处流态改变，水中CO₂逸出，碳酸钙沉淀下来形成边石，久而久之形成一系列凸向水流方向的弧形阶梯状蓄水池。敢沫岩溶洞内的边石坝以“壮乡梯田”为代表，放眼望去，层层叠叠，高低错落。

The rimstone dam is a landscape caused by flowing water at the bottom of the cave. When calcium ion-rich water flows through the uneven bottom of the cave, the flow state changes at the bulge, the CO₂ in the water escapes, and the calcium carbonate precipitates to form rimstone. A series of curved and stepped reservoirs toward the water direction is formed. The rimstone dam in the Ganmoyan karst cave is represented by the “Zhuang terraces”.